A2 OCR Biology Key Terms and Definitions Genomes and Gene Technology

The manipulation of an organism’s DNA to produce an organism or a product that can be made use of in some way.

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Genome

The complete DNA of an organism, or of a species.

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Sequencing (Gene)

Working out the order of nucleotides in a length of DNA.

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Genetic Engineering

Using technology to change the genetic material of an organism.

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Recombinant DNA

DNA that has had DNA from a different source (often from a different species) inserted into it.

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Transformed (Transgenic) Organism

An organism that has had foreign DNA inserted into it.

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Genetically Modified Organism (GMO)

An organism whose DNA has been modified using gene technology – for example, by the removal of some of its genes or by the addition of DNA from another organism.

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Restriction Enzymes

Enzymes produced by bacteria to destroy viral DNA entering the cell; they are widely used in gene technology to cut DNA into smaller lengths.

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Sticky Ends

Short stretches of unpaired nucleotides at the end of a DNA molecule.

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Polymerase Chain Reaction (PCR)

A method of making a large number of copies of a DNA molecule in a relatively short time; it involves the denaturation of DNA (the separation of its two strands), the attachment of a primer and the construction of a DNA strand next to each strand.

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Vector

In gene technology, anything that is used to transfer DNA into the organisms to be genetically transformed; plasmids, viruses and liposomes can be used as vectors.

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Plasmid

A small, circular piece of DNA found in bacteria; plasmids often contain genes for antibiotic resistance, and can be transferred between bacteria.

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Ligase (DNA Ligase)

An enzyme that links nucleotides together by catalysing the formation of covalent bonds between the deoxyribose and phosphate groups.

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Liposome

Tiny ball of liquid, which contains other substances such as DNA or protein.

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Replica Plating

A technique used to determine which of several colonies of bacteria have successfully taken up a plasmid containing the desired gene, by testing for antibiotic resistance.

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Retrovirus

A virus whose genetic material consists of RNA, and which makes DNA using the RNA as a template when it has entered a host cell.

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Promoter

A length of DNA that is needed for a gene to be transcribed.

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Electrophoresis

The separation of fragments of DNA according to their lengths, by applying a voltage across them; the DNA fragments are pulled towards the positive end, smallest first.

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Agarose Gel

A type of agar jelly used in electrophoresis.

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Probe

A short length of DNA that is labelled – for example, by being radioactive; it binds to complementary lengths of DNA and so indicates their position.

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Primer

A short length of DNA with a base sequence complementary to the start of a length of DNA that is to be copied.

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Beta Carotene

An orange pigment found in carrots and in Golden Rice TM , which can be used by the human body to produce retinol.

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Golden Rice TM

A variety of rice that has been genetically engineered to produce large amounts of beta carotene.

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Gene Therapy

Changing the DNA in some of a person’s cells – for example, to attempt to cure a disease caused by faulty genes.

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Somatic Gene Therapy

Gene therapy in which body cells are transformed, but with no effects on cells that will become gametes.

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Germ Line Gene Therapy

Gene therapy that involves changing the DNA in cells whose DNA could be passed on to the next generation.

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Retinol

Vitamin A; a substance required for the formation of the visual pigment rhodopsin.

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Reverse Transcriptase

An enzyme that uses RNA to make a single-stranded molecule of complementary DNA.

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Xenotransplantation

The use of organs from a different species for transplant into humans.

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Annealing

A term used to describe the attachment of a primer to a DNA molecule in PCR.

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CFTR

A protein that acts as a transporter for chloride ions from inside a cell to the outside.